Hybrid drive systems for well stimulation operations

ABSTRACT

In accordance with presently disclosed embodiments, a hybrid drive system that uses multiple sources of mechanical energy to drive a pump is provided. The hybrid drive system may include a first mover for generating first mechanical energy, a pump, a drivetrain for providing first mechanical energy from the first mover to the pump, and a second mover within the drivetrain to generate and provide second mechanical energy to the pump. The multiple sources of mechanical energy may provide flexibility with respect to system design and allow for alternative sources of fuel and energy to be used to drive pumping systems. This may reduce the total diesel fuel consumption necessary to perform a well stimulation operation as well as provide for configurations in which diesel engines may be excluded from the pumping process in favor of alternative energy sources that typically do not have sufficient torque capacity to power a pump.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a U.S. National Stage Application ofInternational Application No. PCT/US2016/050196 filed Sep. 2, 2016,which is incorporated herein by reference in its entirety for allpurposes.

TECHNICAL FIELD

The present disclosure relates generally to treatment operations forhydrocarbon wells, and more particularly, to hybrid drive systems forwell stimulation operations.

BACKGROUND

Hydrocarbons, such as oil and gas, are commonly obtained fromsubterranean formations that may be located onshore or offshore. Thedevelopment of subterranean operations and the processes involved inremoving hydrocarbons from a subterranean formation are complex.Subterranean operations involve a number of different steps such as, forexample, drilling a wellbore at a desired well site, treating andstimulating the wellbore to optimize production of hydrocarbons, andperforming the necessary steps to produce and process the hydrocarbonsfrom the subterranean formation.

Treating and stimulating a well bore can include, among other things,delivering various fluids (along with additives, proppants, gels,cement, etc.) to the wellbore under pressure and injecting those fluidsinto the wellbore. One example treatment and stimulation operation is ahydraulic fracturing operation in which the fluids are highlypressurized via pumping systems to create fractures in the subterraneanformation. The pumping systems typically include high-pressure,reciprocating pumps driven through conventional transmissions by dieselengines, which are used due to their ability to provide high torque tothe pumps. Over the course of a fracturing operation, however, thediesel engines may consume thousands of gallons of diesel fuel, which isexpensive and can be difficult to supply in sufficient quantities in awell site.

BRIEF DESCRIPTION OF THE DRAWINGS

For a more complete understanding of the present disclosure and itsfeatures and advantages, reference is now made to the followingdescription, taken in conjunction with the accompanying drawings, inwhich:

FIG. 1 is a diagram illustrating an example system for treatmentoperations, according to aspects of the present disclosure;

FIG. 2 is a diagram illustrating another example system for treatmentoperations, according to aspects of the present disclosure; and

FIG. 3 is a diagram illustrating an example pumping system, according toaspects of the present disclosure.

DETAILED DESCRIPTION

Illustrative embodiments of the present disclosure are described indetail herein. In the interest of clarity, not all features of an actualimplementation are described in this specification. It will of course beappreciated that in the development of any such actual embodiment,numerous implementation specific decisions must be made to achievedevelopers' specific goals, such as compliance with system related andbusiness related constraints, which will vary from one implementation toanother. Moreover, it will be appreciated that such a development effortmight be complex and time consuming, but would nevertheless be a routineundertaking for those of ordinary skill in the art having the benefit ofthe present disclosure. Furthermore, in no way should the followingexamples be read to limit, or define, the scope of the disclosure.

The terms “couple” or “couples” as used herein are intended to meaneither an indirect or a direct connection. Thus, if a first devicecouples to a second device, that connection may be through a directconnection, or through an indirect mechanical or electrical connectionvia other devices and connections. The term “fluidically coupled” or “influid communication” as used herein is intended to mean that there iseither a direct or an indirect fluid flow path between two components.

The present disclosure is directed to a hybrid drive system that usesmultiple sources of mechanical energy to drive a pump. The multiplesources of mechanical energy may provide flexibility with respect tosystem design and allow for alternative sources of fuel and energy to beused to drive on-site pumping systems. This may reduce the total dieselfuel consumption necessary to perform a well stimulation operation aswell as provide for configurations in which diesel engines may beentirely excluded from the pumping process in favor of alternativemechanical energy sources, such as spark-ignited natural gas engines,that typically do not have sufficient torque capacity to power a wellstimulation pump. Additionally, the use of a second source of mechanicalenergy may increase the useful life of pumping systems by providing asecond system that can account for the reduced output torque that ischaracteristic of aging engines and motors.

FIG. 1 is a diagram illustrating an example system 100 for treatmentoperations, according to aspects of the present disclosure. The system100 includes a fluid management system 110 in fluid communication with ablender system 120. The blender system 120 may in turn be in fluidcommunication with one or more pump systems 130 through a fluid manifoldsystem 140. The fluid manifold system 140 may provide fluidcommunication between the pump systems 130 and a wellbore 150. In use,the fluid management system 110 may receive water or another fluid froma fluid source 115 (e.g., a ground water source, a pond, one or morefrac tanks), mix one or more fluid additives into the received water orfluid to produce a treatment fluid with a desired fluid characteristic,and provide the produced treatment fluid to the blender system 120. Theblender system 120 may receive the produced treatment fluid from thefluid management system 110 and mix the produced treatment fluid with aproppant, such as sand, or another granular material 125 to produce afinal treatment fluid that is directed to the fluid manifold 140. Thepump systems 130 may then pressurize the final treatment fluid togenerate pressurized final treatment fluid that is directed into thewellbore 150, where the pressurized final treatment fluid generatesfractures within a formation in fluid communication with the wellbore150.

An example one of the pump systems 130 may comprise a first mover 130 a,a pump 130 b, and a drive train 130 c. As used herein, a mover maycomprise any device that converts energy into mechanical energy to drivea pump. Example movers include, but are not limited to, electric motors,hydrocarbon-driven or steam engines, turbines, etc. The drive train 130c may be removably coupled to the first mover 130 a and the pumps 130 bthrough one or more drive shafts (not shown), and may comprise atransmission 130 d with one or more gears that transmits mechanicalenergy from the first mover to the pump 130 b. For instance, to theextent the pumps 130 b comprise reciprocating pumps, the mechanicalenergy may comprise torque that drives the pump 130 b.

The drive train 130 c may further comprise a second mover 130 e. Asdepicted, the second mover 130 e is coupled to the transmission 130 dbetween the transmission 130 d and the pump 130 b. In the embodimentshown, the second mover 130 e may receive mechanical energy from thefirst mover 130 a through the transmission 130 d and provide thereceived mechanical energy to the pump 130 b augmented by mechanicalenergy generated by the second mover 130 e. It should be appreciated,however, that the orientation of the second mover 130 e with respect tothe first mover 130 a, transmission 130 d, and the pump 130 b is notlimited to the embodiment shown. In other embodiments, the second mover130 e may be positioned between the transmission 130 d and the firstmover 130 a, for instance, or between elements of the transmission 130 ditself. In yet other embodiments, the second mover 130 e may beincorporated into the transmission 130 d as part of a hybridtransmission system through which power from both the first mover 130 aand second mover 130 e are provided to the pump 130 b.

The first mover 130 a and second mover 130 e may receive energy or fuelin one or more forms from sources at the wellsite. The energy or fuelmay comprise, for instance, hydrocarbon-based fuel, electrical energy,hydraulic energy, thermal energy, etc. The sources of energy or fuel maycomprise, for instance, on-site fuel tanks, mobile fuel tanks deliveredto the site, electrical generators, hydraulic pumping systems, etc. Thefirst mover 130 a and second mover 130 e may then convert the fuel orenergy into mechanical energy that can be used to drive the associatedpump 130 b.

In the embodiment shown, the first mover 130 a may comprise an internalcombustion engine such as a diesel or dual fuel (e.g., diesel andnatural gas) engine and the second mover 130 e may comprise an electricmotor. The internal combustion engine 130 a may receive a source of fuelfrom one or more fuel tanks (not shown) that may located within thepumping system 130 and refilled as necessary using a mobile fuel truckdriven on site. The electric motor 130 e may be electrically coupled toa source of electricity through a cable 130 f. Example sources ofelectricity include, but are not limited to, an on-site electricalgenerator, a public utility grid, one or more power storage elements,solar cells, wind turbines, other power sources, or one or morecombinations of any of the previously listed sources.

As depicted, the source of electricity coupled the second mover 130 ecomprises a generator 160 located at the well site. The generator maycomprise, for instance, a gas-turbine generator or an internalcombustion engine that produces electricity to be consumed or stored onsite. In the embodiment shown, the generator 160 may receive and utilizenatural gas from the wellbore 150 or from another wellbore in the field(i.e., “wellhead gas”) to produce the electricity. As depicted, thesystem 100 may include gas conditioning systems 170 that may receive thegas from the wellbore 150 or another source and condition the gas foruse in the generator 160. Example gas conditioning systems include, butare not limited to, gas separators, gas dehydrators, gas filters, etc.In other embodiments, conditioned natural gas may be transported to thewell site for use by the generator.

The system 100 may further include one or more energy storage devices180 that may receive energy generated by the generator 160 or otheron-site energy sources and store in one or more forms for later use. Forinstance, the storage devices 180 may store the electrical energy fromthe generator 160 as electrical, chemical, or mechanical energy, or inany other suitable form. Example storage devices 180 include, but arenot limited to, capacitor banks, batteries, flywheels, pressure tanks,etc. In certain embodiments, the energy storage devices 180 andgenerator 160 may be incorporated into a power grid located on sitethrough which at least some of the fluid management system 110, blendersystem 120, pump systems 130, and gas conditioning systems 170 mayreceive power.

In use, the first mover 130 a and second mover 130 e may operate inparallel or in series to drive the pump 130 b, with the division ofpower between the movers being flexible depending on the application.For instance, in a multi-stage well stimulation operation, the formationmay be fractured (or otherwise stimulated) in one or more “stages,” witheach stage corresponding to a different location within the formation.Each “stage” may be accompanied by an “active” period during which thepumps are engaged and pressurized fluids are being pumped into thewellbore 150 to fracture the formation, and an “inactive” period duringwhich the pumps are not engaged while other ancillary operations aretaking place. The transition between the “inactive” and “active” periodsmay be characterized by a sharp increase in torque requirement.

In an embodiment in which the first mover 130 a comprises a dieselengine and the second mover 130 e comprises an electric motor, both thediesel engine and electric motor may be engaged to provide the necessarypower, with the percentage contribution of each depending on the periodin which the system 100 is operating. For instance, during the“inactive” and “active” periods in which the torque requirements arerelatively stable, the diesel engine, which operates more efficientlyduring low or near constant speed operations, may provide a higherpercentage (or all) of the torque to the pump than the electric motor.In contrast, during transitions between “inactive” and “active” states,the electric motor may supplant the diesel engine as the primary sourceof torque to lighten the load on the diesel engine during thesetransient operations. In both cases, the electric motor reduces thetorque required by the diesel engine, which reduces the amount of dieselfuel that must be consumed during the well stimulation operation. Itshould be noted that power sources could be used during continuousoperation or intermittently as needed, including during transmissiongear-shift events.

In addition to reducing the amount of diesel fuel needed to perform awell stimulation operation, the use of a first mover and a second moverin a pump system described herein may provide flexibility with respectto the types of movers that may be used. For instance, natural gasengines, i.e., internal combustion engines that use natural gas as theironly source of combustion, are typically not used in oil fieldenvironments due to their limited torque capacity. By including twomovers within the pump system 130, the torque capacity of the naturalgas engine may be augmented to allow the use of a natural gas enginewithin the pump system 130. For instance, in certain embodiments, thefirst mover 130 a may comprise a natural gas engine and the second mover130 e may comprise an electric motor that operates in series or parallelwith the natural gas engine to provide the necessary torque to power thepump 130 b.

In certain embodiments, the pump systems 130 may be electrically coupledto a controller 190 that directs the operation of the first and secondmovers of the systems 130. The controller 190 may comprise, forinstance, an information handling system that sends one or more controlsignals to the pump systems 130 to control the speed/torque output ofthe first and second movers. As used herein an information handlingsystem may comprise any system containing a processor and a memorydevice coupled to the processor containing a set of instructions that,when executed by the processor, cause the processor to perform certainfunctions. The control signals may take whatever form is necessary tocommunicate with the associated mover. For instance, a control signal toan electric motor may comprise an electrical control signal to avariable frequency drive coupled to the electric motor, which mayreceive the control signal and alter the operation of the electric motorbased on the control signal. In certain embodiments, the controller 190may also be electrically coupled to other elements of the system,including the fluid management system 110, blender system 120, pumpsystems 130, generator 160, and gas conditioning systems 170 in order tomonitor and/or control the operation of the entire system 100. In otherembodiments, some or all of the functionality associated with thecontroller 190 may be located on the individual elements of the system,e.g., each of the pump systems 130 may have individual controllers thatdirect the operation of the associated first and second movers.

It should be appreciated that only one example configuration isillustrated in FIG. 1 and that other embodiments and configurations arepossible, depending on the types of movers and energy or fuel. Incertain embodiments, some or all of the pumping systems 130 may includethe same configuration, including the same types of first and secondmovers. The configurations of the individual pumping systems 130 and ofthe pumping systems generally may depend, for instance, on the availablefuel and energy sources at the well site. For example, if a source ofnatural gas is more readily available than diesel fuel at a particularwell site, the pumping systems 130 may be configured to utilize naturalgas as a source of fuel/energy for both the first and second movers,which could include the use of a dual fuel or natural gas driven engineas the first mover and an electric motor powered by a natural-gas drivengenerator as the second mover.

In certain embodiments, excess energy generated by the pumping systems130 or other elements within the system 100 may be used as an energysource for the first and/or second movers. The excess energy may be usedinstead of or in addition to any of the energy and fuel sourcesdescribed above. FIG. 2 is a diagram illustrating another example system200 for treatment operations in which the excess energy is utilized,according to aspects of the present disclosure. As can be seen, thesystem 200 comprises similar pumping systems 240 to those describedabove with respect to FIG. 1. Notably, each of the pumps systems 240 maycomprise a first mover 240 a, a pump 240 b and a drivetrain 240 ccomprising a transmission 240 d and a second mover 240 e. The secondmovers of the pumping systems 240 may comprise electric motors thatfunction similarly to the electric motor described above with respect toFIG. 1.

In the embodiment shown, the second movers of the pumping systems 240may themselves comprise sources of energy for the system 200. Inparticular, as can be seen, the second movers of the pumping systems 240may be coupled to each other and to an energy storage device 280. Duringinactive periods, or periods with lower torque requirement by the pumps,the first movers of the system 200 may generate excess energy,particularly when the first movers comprise diesel engines that are leftidling during “inactive” periods. During those periods, some or all ofthe second movers may function as generators, receiving the excessenergy from the first movers and converting that excess energy intoanother form of energy for immediate use by other ones of the secondmovers within the system or for storage within the energy storage device280. For instance, where the first movers comprise diesel engines andthe second movers comprise electric motors, some or all of the electricmotors may also function as electric generators used to generateelectricity using the excess torque generated by the diesel engines, andthat electricity may be consumed by other ones of the electric motors toimmediately reduce the fuel consumption of the associated diesel enginesand/or stored in the energy storage device 280 for later use.

Similarly, where the first movers comprise diesel engines and the secondmovers comprise hydraulic motors driven by pressurized hydraulic fluids,some or all of the hydraulic motors may use excess torque generated bythe diesel engines to pressurize the hydraulic fluids for use by otherones of the hydraulic motors within the system 200 and/or for storagewithin the energy storage device 280 in the form of pressurized tank ofhydraulic fluid. Other configurations are possible within the scope ofthis disclosure.

The embodiment show in FIG. 2 could also be used to increase the load onthe engines (e.g., first movers) when the system is operating in coldambient temperatures. The increased load may help to raise the exhausttemperatures of the engines during cold weather. This may enable heatsensitive aftertreatment emission devices to operate more efficientlyand reliably, with less clogging of those systems as experienced duringlight loading of the engine with low exhaust temperatures. The excessmotive energy output from the pumping systems 240 during this coldweather operation of the pumps may be converted into another form ofenergy via the second movers for immediate use by one of the othersecond movers or for storage in the energy storage device 280 for lateruse.

FIG. 3 illustrates an example pumping system 300, according to aspectsof the present disclosure. The pumping system 300 may be used, forinstance, as one or more of the pumping systems described above withreference to FIGS. 1 and 2. As depicted, the system 300 comprises afirst mover 302 in the form of a diesel engine coupled to areciprocating pump 304 through a hybrid transmission system 306 intowhich a second mover in the form of an electric motor (or electricmotor/generator) is integrated. The first mover 302, pump 304, andtransmission system 306 are mounted on a trailer 308 coupled to a truck310. The truck 310 may comprise, for instance, a conventional enginethat provides locomotion to the truck 310 and trailer 310 through ahybrid transmission incorporating an electric motor or hydraulic system.The system 300 may further comprise an electrical connection 312, suchas a cable, between the hybrid transmission of the truck 310 and thesecond mover in the pump transmission system 306.

In use, the truck 310 and trailer 308 with the pumping equipment mountedthereon may be driven to a well site at which a fracturing or othertreatment operation will take place. In certain embodiments, the truck310 and trailer 308 may be one of many similar trucks and trailers thatare driven to the well site. Once at the site the pump 304 may befluidically coupled to a wellbore (not shown), such as through a fluidmanifold, to provide treatment fluid to the wellbore. The pump 304 mayfurther be fluidically coupled to a source of treatment fluids to bepumped into the wellbore. When connected, the diesel engine may bestarted to provide a primary source of torque to the pump 304 throughthe pump transmission system 306. The electric motor in the pumptransmission system 306 similar may be engaged to provide a supplementalsource of torque to the pump 304. As depicted, the electric motor in thepump transmission system 306 may receive energy directly from the hybridtransmission of the truck 310, such that the truck itself operates as anelectrical generator for the pumping operation. In addition to energyfrom the truck 310 and the electric motor in the pump transmissionsystem 306, the pump may receive electricity from other energy sourceson the site, including a dedicated electrical generator on site or otherpumping systems located on the site.

Embodiments disclosed herein include:

A. An apparatus including a first mover for generating first mechanicalenergy, a pump, a drivetrain, and a second mover. The drivetrainprovides the first mechanical energy from the first mover to the pump,and the second mover is disposed within the drivetrain to generate andprovide second mechanical energy to the pump.

B. A system including a first pump system including a first mover forgenerating first mechanical energy, a pump, a drivetrain for providingfirst mechanical energy from the first mover to the pump, and a secondmover within the drivetrain to generate and provide second mechanicalenergy to the pump. The system also includes a fluid manifold providingfluid communication between the pump and a wellbore, and at least one ofa fluid management system and a blender unit providing a source oftreatment fluids to the pump.

C. A method including generating first mechanical energy with a firstmover mechanically coupled to a pump, generating second mechanicalenergy with a second mover mechanically coupled to the pump, anddirecting fluid from the pump to a wellbore using the first mechanicalenergy and the second mechanical energy.

Each of the embodiments A, B, and C may have one or more of thefollowing additional elements in combination: Element 1: wherein thefirst mover includes one of a diesel engine or a dual fuel engine andthe second mover includes at least one of an electric motor and ahydraulic motor. Element 2: wherein the first mover includes a naturalgas spark-ignited engine and the second mover includes at least one ofan electric motor and a hydraulic motor. Element 3: wherein thedrivetrain includes a transmission and the second mover is coupledbetween the first mover and the transmission or between the transmissionand the pump. Element 4: wherein the drivetrain includes a hybridtransmission into which the second mover is integrated. Element 5:wherein the pump includes a hybrid pump into which the second mover isintegrated. Element 6: further including a trailer onto which the firstmover, pump, drivetrain and second mover are mounted, and a truckcoupled to the trailer, wherein the truck includes a diesel engine and ahybrid transmission with an integrated electric generator. Element 7:wherein the second mover is coupled to and receives energy from theintegrated electric generator of the hybrid transmission.

Element 8: further including an energy storage device to provide asource of energy to at least one of the first mover and the second moverto generate the respective first and second mechanical energy. Element9: further including an electrical generator coupled to the energystorage device and at least one of the first mover and the second mover.Element 10: further including a gas conditioning system to receivenatural gas from a wellbore and provide conditioned natural gas to theelectrical generator from which the electrical generator generateselectricity. Element 11: further including a second pump system with another first mover, an other pump, an other drivetrain, and an othersecond mover. Element 12: wherein the second mover and the other secondmover include electric motors electrically connected to share electricalenergy. Element 13: wherein the electric motors are further electricallyconnected to an energy storage system for providing electricity to atleast one of electric motors and storing energy generated by at leastone electric generator.

Element 14: further including receiving the first mechanical energy atthe pump through a drivetrain coupled between the first mover and thepump. Element 15: wherein generating second mechanical energy with thesecond mover includes generating second mechanical energy within thedrivetrain. Element 16: wherein the first mover includes at least one ofa diesel engine, a dual fuel engine, and a spark-ignited natural gasengine. Element 17: wherein the second mover includes at least one of anelectric motor and a hydraulic motor. Element 18: wherein generatingsecond mechanical energy with the second mover includes receiving atleast one of electricity and pressurized hydraulic fluid from an energystorage device coupled to the second mover.

Although the present disclosure and its advantages have been describedin detail, it should be understood that various changes, substitutionsand alterations can be made herein without departing from the spirit andscope of the disclosure as defined by the following claims.

What is claimed is:
 1. An apparatus, comprising: a first mover forgenerating first mechanical energy, wherein the first mover comprises aninternal combustion engine; a well stimulation pump comprising areciprocating pump; a drivetrain for providing the first mechanicalenergy from the first mover to the well stimulation pump; and a secondmover within the drivetrain to generate and provide second mechanicalenergy to the well stimulation pump, wherein the second mover comprisesat least one of an electric motor and a hydraulic motor; wherein thedrivetrain outputs the first mechanical energy and the second mechanicalenergy directly to the well stimulation pump, the combined first andsecond mechanical energies providing a torque sufficient to drive thewell stimulation pump to pump fluid to a wellbore.
 2. The apparatus ofclaim 1, wherein the first mover comprises one of a diesel engine or adual fuel engine.
 3. The apparatus of claim 1, wherein the first movercomprises a spark-ignited natural gas engine.
 4. The apparatus of claim1, wherein the drivetrain comprises a transmission and the second moveris coupled between the first mover and the transmission or between thetransmission and the pump.
 5. The apparatus of claim 1, wherein thedrivetrain comprises a hybrid transmission into which the second moveris integrated.
 6. The apparatus of claim 1, wherein the pump comprises ahybrid pump into which the second mover is integrated.
 7. The apparatusof claim 1, further comprising a trailer onto which the first mover,pump, drivetrain and second mover are mounted; and a truck coupled tothe trailer, wherein the second mover is coupled to and receives energyfrom the truck.
 8. The apparatus of claim 1, wherein the drivetrainprovides the first mechanical energy and the second mechanical energyadded together to the pump.
 9. A system, comprising: a first pump systemcomprising a first mover for generating first mechanical energy, whereinthe first mover comprises an internal combustion engine; a pump; adrivetrain for providing first mechanical energy from the first mover tothe pump; and a second mover within the drivetrain to generate andprovide second mechanical energy to the pump, wherein the second movercomprises at least one of an electric motor and a hydraulic motor;wherein the drivetrain outputs the first mechanical energy and thesecond mechanical energy directly to the pump; a fluid manifoldproviding fluid communication between the pump and a wellbore; and atleast one of a fluid management system and a blender unit providing asource of treatment fluids to the pump.
 10. The system of claim 9,further comprising an energy storage device to provide a source ofenergy to at least one of the first mover and the second mover togenerate the respective first and second mechanical energy.
 11. Thesystem of claim 10, further comprising an electrical generator coupledto the energy storage device and at least one of the first mover and thesecond mover.
 12. The system of claim 11, further comprising a gasconditioning system to receive natural gas from a wellbore and provideconditioned natural gas to the electrical generator from which theelectrical generator generates electricity.
 13. The system of claim 9,further comprising a second pump system with an other first mover, another pump, an other drivetrain, and an other second mover.
 14. Thesystem of claim 13, wherein the second mover and the other second movercomprise electric motors electrically connected to share electricalenergy.
 15. The system of claim 14, wherein the electric motors arefurther electrically connected to an energy storage system for providingelectricity to at least one of electric motors and storing energygenerated by at least one electric generator.
 16. The system of claim 9,wherein the first mover comprises at least one of a diesel engine, adual fuel engine, and a spark-ignited natural gas engine.
 17. A method,comprising: generating first mechanical energy with a first movermechanically coupled to a pump, wherein the first mover comprises aninternal combustion engine; generating second mechanical energy with asecond mover mechanically coupled to the pump, wherein the second movercomprises at least one of an electric motor and a hydraulic motor; anddirecting fluid from the pump to a wellbore using the first mechanicalenergy and the second mechanical energy.
 18. The method of claim 17,further comprising receiving the first mechanical energy at the pumpthrough a drivetrain coupled between the first mover and the pump,wherein generating second mechanical energy with the second movercomprises generating second mechanical energy within the drivetrain. 19.The method of claim 17, wherein the first mover comprises at least oneof a diesel engine, a dual fuel engine, and a spark-ignited natural gasengine.
 20. The method of claim 17, wherein generating second mechanicalenergy with the second mover comprises receiving at least one ofelectricity and pressurized hydraulic fluid from an energy storagedevice coupled to the second mover.